linux-kernel - Re: Lack of suspend/resume/shutdown ordering between GPIO providers and consumers

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Date:   Wed, 25 Apr 2018 13:47:22 -0500
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <dmitry.torokhov@...il.com>,
        <jeffy.chen@...k-chips.com>, <enric.balletbo@...labora.com>,
        <josephl@...dia.com>, <opendmb@...il.com>, <rjw@...ysocki.net>
Subject: Re: Lack of suspend/resume/shutdown ordering between GPIO providers
 and consumers



On 04/25/2018 01:29 PM, Florian Fainelli wrote:
> On 04/25/2018 11:06 AM, Grygorii Strashko wrote:
>>
>>
>> On 04/24/2018 05:58 PM, Florian Fainelli wrote:
>>> Hi Linus, Rafael, all
>>>
>>> Our GPIO controller driver: gpio-brcmstb.c has a shutdown callback which
>>> gets invoked when the system is brought into poweroff aka S5. So far so
>>> good, except that we also wish to use gpio_keys.c as a possible wake-up
>>> source, so we may have a number of GPIO pins declared as gpio-keys that
>>> allow the system to wake-up from deep slumber.
>>>
>>> Recently we noticed that we could easily get into a state where
>>> gpio-brcmstb.c::brcmstb_gpio_shutdown() gets called first, and then
>>> gpio_keys.c::gpio_keys_suspend() gets called later, which is too late to
>>> have the enable_irq_wake() call do anything sensible since we have
>>> suspend its parent interrupt controller before. This is completely
>>> expected unfortunately because these two drivers are both platform
>>> device instances with no connection to one another except via Device
>>> Tree and the use of the GPIOLIB APIs.
>>
>> You can take a look at device_link_add() and Co.
> 
> OK, though that requires a struct device references, so while I could
> certainly resolve the device_node -> struct device that corresponds to
> the GPIO provider , that poses a number of issues:
> 
> - not all struct device_node have a corresponding struct device
> reference (e.g: clock providers, interrupt controllers, and possibly
> other custom drivers), though in this case, they most likely do have one
> 
> - resolving a struct device associated with a struct device_node is
> often done in a "bus" specific way, e.g: of_find_device_by_node(), so if
> the GPIO provider is e.g: i2c_device, pci_device etc. etc. this might
> not work that easily
> 
> I think this is what Dmitry just indicated in his email as well.
> 
>>
>> But it's little bit unclear what exactly you have issue with:
>> - shutdown
>> - suspend
>>
>> above are different (at least as it was before) and gpio-brcmstb.c
>>   brcmstb_gpio_shutdown() should not be called as part of suspend !?
>> may be you mean brcmstb_gpio_suspend?
> 
> The issue exists with shutdown (through the use of "poweroff"), that is
> confirmed, but I cannot see how it does not exist with any suspend state
> as well, for the same reason that the ordering is not strictly enforced.

Sry, but it still required some clarification :( - poweroff calls
device_shutdown() which, in turn, should not call .suspend(), so
how have you got both .shutdown() and .suspend() callbacks called during
poweroff? Am I missing smth?

Note. Suspend and shutdown uses different dev lists:
- shutdown uses kset
- suspend uses dpm_list

-- 
regards,
-grygorii